A universal challenge faced by all living organisms is to identify and then attempt to counteract the deleterious effects of environmental stresses. Whether multicellular or unicellular, all organisms have evolved mechanisms to deal with such molecular insults. Indeed the fundamental mechanisms for responding to such agents as ionizing radiation, oxidative stress, mutagenic and toxic small molecules, nutrient deprivation and temperature extremes (heat shock) have been highly and evolutionarily conserved at the molecular level. A cardinal feature of all of these molecular-cellular protective mechanisms is the induction of the transcription of certain cellular genes encoding proteins that confer stress-protective properties. Concomitantly, transcription of genes encoding proteins (and RNAs) that lack protective cellular/molecular effects is repressed. These critical transcriptional responses are all mediated through the actions of a handful of distinct transcriptional activator and repressor proteins. In this study, the investigators propose to use state-of-the-art multidimensional tandem mass spectrometry methods to identify and characterize the protein-protein regulatory networks connecting the environment with key conserved transcription factors known to drive the gene-level protective changes in cellular RNA synthesis. The studies will initially focus on the genetically tractable and simple eukaryote Baker's yeast (Saccharomyces cerevisiae). However, in the latter phase of this project, they will apply the knowledge gained in the unicellular yeast model system to human cells.